main.dart

typedef RawDocument = Map<String,dynamic>;
typedef RawCollection = Iterable<RawDocument>;

void main() async {
  final y = await _getIterable();
  print(y);
  print(y.runtimeType);
}

Future<RawCollection> _getIterable() async {
  final Iterable<Map<Object?,dynamic>> list = [ //Iterable<Map> should also work
    {
      "x":5,
      "y":"hi",
    },
    {
      "x":6,
      "y":"hello",
    }
  ];
  return await Future.value(list.map((e)=>e.cast<String,dynamic>()));
}